Androgens regulate gene expression in non-genital tract tissues by a mechanism similar to that by which they mediate male sexual development in primary target tissues. The mouse kidney provides a useful model system for studying the molecular genetics of the regulation of gene expression by androgens. Gus-s is the structural gene of the beta-glucuronidase genetic complex [Gus], for which many naturally occurring structural and regulatory mutations have been identified by classical genetic analysis. DNA sequence analysis of alleles of Gus-s has led to the identification of candidates for the identification of Gus-r, the cis-acting regulatory locus that influences the response of Gus-s to androgen treatment. Kap, the gene for kidney androgen-regulated protein (KAP), is expressed in the same cells in the kidney as Gus-s, but is regulated very differently by androgens. Kap also exhibits differential regulation of its expression in two anatomically distinct regions of the proximal tubules. Hybridization histochemistry revealed that Kap is regulated by estrogen in the proximal tubules. Hybridization histochemistry revealed that Kap is regulated by estrogen in the proximal tubule epithelial cells of the S3 segment in the outer medulla. The physiological significance of the unusual regulatory pattern of Kap expression by sex steroids is presently unknown. Our proposed studies will focus on the unique features of the regulation of these two genes by androgens. This will be accomplished by identification of the transfer studies and by analysis of specific DNA-protein binding in vitro. The cell-specific expression of Kap and its regulation by sex steroids will be studied by hybridization in situ and immunohistochemistry. The mechanism of androgen action will be investigated in a cell-free transcription system using these promoters as templates for transcription initiation. Finally, nuclear proteins that interact with cis-acting sites adjacent to the androgen responsive elements and those that interact directly with the androgen receptor to affect transcription will be identified. Cloned cDNAs for these proteins will be isolated for their structural characterization as well as for a source of protein for functional studies in the cell-free transcription assay. This research plan will lead to new, significant data in the molecular mechanisms involved in androgen action.